The invention relates generally to a heat transfer device and, more particularly, to a heat transfer enhancing system for improving the heat transfer characteristics on various surfaces of the heat transfer device.
A heat transfer device, such as a heat exchanger, is a device that transmits thermal energy between a hot fluid and a cold fluid. Heat flows from the hot fluid to the cold fluid in the heat transfer device via a plurality of heat transfer surfaces such as tubes or panels. Heat exchangers may be classified into different types such as parallel flow type, counter flow type, cross flow type, single pass type, or multiple pass type. Heat exchangers used in fluid processing plants, for example liquid natural gas vaporizers or natural gas liquefiers, rely on several conventional heat transfer techniques to enhance thermal effectiveness or to enhance other heat transfer characteristics between a process fluid (e.g. liquid natural gas) side and a heat source or a heat sink side of the heat exchanger.
One conventional technique to improve thermal effectiveness involves increasing the surface area of the heat transfer surfaces. An increase in the surface area may be achieved by providing a plurality of fins, protrusions, or recesses for example, to the heat transfer surfaces, leading to an increase in the total heat flux per unit area (base surface area) of the heat transfer device resulting in a decrease in size and cost of the heat transfer device or an increase in total capacity of the device.
Another conventional technique to improve thermal effectiveness is to increase the heat transfer coefficient by providing flow turbulators or baffles to the heat transfer surfaces. However, provision of flow turbulators or baffles results in increased pressure losses in the heat transfer device.
Accordingly, there is a need for a system and a method to increase thermal effectiveness in a heat transfer device, while maintaining compact size and acceptable pressure losses.